Conventionally, when an ECU (electronic control unit) including a circuit substrate such as a printed substrate is manufactured, a connector portion including a connector terminal is prepared first. The connector terminal is formed in the connector portion by press-fitting or insert-molding to be used for external connection. The connector terminal is attached to the circuit substrate. The connector portion as a cover (lid) of a casing is inserted into an opening part of the casing to seal the casing while the circuit substrate is housed in the casing. An electric connection box including the ECU having such configuration is known. For example, Patent Document 1 (JP 2012-235578), Patent Document 2 (JP 2007-073321) and Patent Document 3 (JP 2014-217104) show such electric connection boxes.
In Patent Document 1, a connector portion and a circuit substrate are fixed to each other by screwing. As compared to a case where a connector portion and a circuit substrate are connected each other only through a soldered part, a stress acted on the soldered part can be reduced. However, in this case, the screwing is necessary. Therefore, the number of components such as a screw is increased, and the number of manufacturing steps such as a screwing step is also increased.
In Patent Documents 2 and 3, a connector terminal is in contact with and supported by a casing. Hence, a stress acted on a soldered part between the connector terminal and a circuit substrate can be reduced without screwing. However, in this case, an assembly of the connector terminal to the circuit substrate is performed after electronic components are attached to the circuit substrate in a reflow process. Hence, soldering to electrically connect the connector terminal and the circuit substrate is performed in a flow process after the reflow process. As a result, soldering is performed twice (i.e. the reflow process and the flow process are performed).
Patent Document 4 (JP 2014-110224) has proposed a structure in which soldering of electronic components or a connector terminal to a circuit substrate can be performed by a single reflow process.
When soldering of the electronic components to the circuit substrate and soldering of the connector terminal to the electronic components are performed simultaneously in the reflow process, the circuit substrate is transferred to a reflow step in a state where the connecter terminal of a connector portion is inserted into a through-hole of the circuit substrate. The connector portion functioning as the cover (lid) of the casing, shown by Patent Document 1 to 3, has a size to close the opening part of the casing, i.e. larger than the circuit substrate in a direction along the circuit substrate. Hence, the circuit substrate is transferred in a state where the connector portion extends outward of the circuit substrate in the direction along the circuit substrate. Therefore, in order to protect the circuit substrate and the connector portion during the transferring and to secure a space for the transferring, it is necessary to provide a transfer space, so-called “ear”, surrounding the circuit substrate and the connector portion.
For example, FIG. 10 is a diagram showing a multiple-set substrate including multiple circuit substrates J1. A connector portion J2 is attached to each circuit substrate J1, and a transfer space J3 is provided to surround all of the circuit substrates J1 and the connector portions J2. In this case, the electronic components and the connecter terminal can be soldered to the circuit substrate in the reflow process at a time. However, the transfer space may be necessary, and a size of a substrate, such as the multiple-set substrate, may be required to be enlarged. Thus, the number of circuit substrates per unit area may decrease, and a manufacturing cost may increase. Further, the connector portion is subjected to high temperature in the reflow process, and the connector portion may need to be made of heat-resistant resin. Thus, a degree of freedom of material selection may reduce, and a cost of the connector portion may increase.
When the structure of the electric connection box without screwing as in Patent Documents 2 and 3 and the reflow process as in Patent Document 4 where the electronic components and the connector terminal are soldered to the circuit substrate simultaneously are combined, effects due to omission of a screwing step may be obtained, but a cost reduction effect may not be obtained or a cost may increase.